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Walking on the Moon

Day length and circadian rhythms


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I was reminded today of some research I read about a while ago that our natural body clock does not quite align to an Earth day.  There was an experiment done some time back suggesting our "natural" day length was nearer 25 hours, but I believe that has been discredited.  Even so, we still have a tendency to fall into a daily rhythm that is a little longer than 24 hours when deprived of outside stimuli that allow us to resynchronise with the Sun.

As far as I can find out, Earth day lengths are actually getting longer and the rate of change is slow.  That is, historically day lengths have been shorter than they are now but they haven't changed hugely in our human evolutionary timescale (though perhaps they have done so more obviously in mammalian evolutionary timescales).

I'd naively expect that we would have evolved to have a body clock that was closely aligned to our planetary day length to the point where it seems very strange to me that there doesn't appear to be an obvious correlation and in fact is longer than historical day lengths.

Has anyone come across any pausible explanation for this disparity?

I'm a hardcore night owl and my subjective experience is that I do tend to drift later and later into the small hours when left to my own devices, at least to the point where it becomes significantly objectionable to those around me.  Are there people who always seem to want to go to sleep earlier and earlier in the evening as well?

My personal ideal would probably be to stay up as late as I feel comfortable with and then go to bed leaving the curtains open, to be woken by the daylight when I was ready.  Sadly that doesn't seem to fit in with modern society.  I might be a dinosaur, but for the fact that if that were that true my natural body clock ought to be several hours shorter than it actually is :D


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I can never got used to the long days of midsummer - no matter how hard I try(ied). I tend to sleep better and feel more psychologically balanced when I'm in a country/place with somewhat moderate day length, or when it's autumn or spring (or even early summer). I was offered a position at the University of Glasgow a month ago and had to turn it down because I know I won't cope well with the very long summer days. That's the curse of having lived in several countries, I guess. Your body rhythm gets irreversibly messed up. Or, I'm just weird! 

Edited by emadmoussa
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I am in Sweden at the moment and it does not get dark ...... I haven’t sleapt for over three days ☀️ The crazily hot temperatures are not helping, fortunately though I will be flying back home in a few hours so I will get some long awaited ?

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I think it's because of our unnatural environment. We spend a lot of time indoors, unlike our ancestors, so are confused by artificial lights (and curtains blocking out sunlight). I'm sure if we lived outdoors it'd be different...

...if it wasn't for light pollution. Everything is the fault of light pollution!!

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